Aluminum as a bi-functional reducing agent for the fabrication of graphene encapsulated silicon microspheres as anodes for high-performance lithium-ion batteries

The composites of reduced graphene oxide (rGO) encapsulated porous silicon (P-Si) microspheres are constructed using metallic aluminum as a bi-functional reducing agent at low temperatures. The preparation process of P-Si is carried out in a special reactor at 300 °C. For the reaction, SiO 2 is used as the silicon source and AlCl 3 is added to maintain the smooth progress of the thermite reduction reaction. Subsequently, graphene oxide is reduced by aluminum powder in an acidic liquid phase system and then the P-Si/rGO composite material is constructed by freeze-drying technique. As a kind of promising anode for lithium-ion batteries (LIBs), the porous structure of silicon microspheres can relieve the internal stress caused by volume expansion and shorten the diffusion path of lithium ions during charge/discharge processses. The flexible graphene layers can adapt the volume effect of the P-Si microspheres and therefore maintain the structural stability of the composites and enhance the electrical conductivity . The obtained P-Si/rGO composite material exhibits excellent electrochemical performance, which can maintain a superior capacity of 837 mAh g −1 upon 500 cycles under a current density of 0.5 A g −1 and exhibit satisfied cycling stability with a capacity of 704 mAh g −1 after 1000 cycles at a 1 A g −1 current density.